The present invention relates generally to engine exhaust gas mufflers, and more particularly provides a uniquely configured exhaust gas muffler, and associated sound attenuating methods, for effectively attenuating both core and turbine noise generated by a gas turbine engine.
In many gas turbine engine applications, particularly those in which the engine is used in conjunction with a ground vehicle or in a stationary ground installation, effective attenuation of the engine's exhaust noise becomes highly important. In general, to satisfactorily diminish a turbine engine's exhaust noise, both its core and turbine noise must be attenuated. Core noise is a low frequency noise component believed to be at least partly caused by the combustion processes within the engine, while turbine noise is a high frequency noise component caused by the interaction of high velocity gasses with the engine's turbine section or sections. The frequency spectrum of core noise is essentially broadband, peaking at a relatively low frequency around 200 to 800 HZ where most of the energy of such core noise is concentrated. Turbine noise, on the other hand, is a significantly higher frequency noise phenomenon, having both broadband and discrete spectral components, peaking at a relatively high frequency around 6,000 to 10,000 HZ.
To effect a satisfactory degree of silencing of both of these exhaust noise components, conventional exhaust gas mufflers for turbine engines have been constructed with various sound attenuating devices placed end-to-end along the flow axis of the muffler, each such device being designed to attenuate engine exhaust noise across a different frequency band. Because of this conventional necessity of arranging different attenuating devices in such end-to-end relationship, conventional gas turbine engine exhaust mufflers have evolved into relatively large and bulky structures - sometimes approaching the overall size of the engines whose exhaust noise they are designed to attenuate.
Accordingly, it is an object of the present invention to provide a turbine engine exhaust gas muffler which will function to effectively attenuate both core and turbine noise, yet be considerably more compact than conventional mufflers.